\(\frac{5}{6}+\frac{14}{15}=\frac{25}{30}+\frac{28}{30}=\frac{53}{30}\)

   5/6 +14/15

=25/30 + 28/30

=         53/30

= 5/6 x (1/5 + 4/5 - 1)
= 5/6 x 0 = 0

\(\dfrac{5}{6}\times\dfrac{7}{5}+\dfrac{5}{6}:\dfrac{15}{3}+\dfrac{5}{6}\times\dfrac{3}{5}-\dfrac{5}{6}\\ =\dfrac{5}{6}\times\dfrac{7}{5}+\dfrac{5}{6}\times\dfrac{1}{5}+\dfrac{5}{6}\times\dfrac{3}{5}-\dfrac{5}{6}\\ =\dfrac{5}{6}\times\left(\dfrac{7}{5}+\dfrac{1}{5}+\dfrac{3}{5}-1\right)\\ =\dfrac{5}{6}\times\dfrac{6}{5}=1\)

a: \(=\dfrac{5}{14}\left(\dfrac{2}{9}+\dfrac{7}{9}+1\right)=\dfrac{5}{14}\cdot2=\dfrac{5}{7}\)

b: \(=\dfrac{6}{8}\left(\dfrac{6}{7}-6\right)=\dfrac{6}{8}\cdot\dfrac{-36}{7}=\dfrac{-216}{56}=\dfrac{-27}{7}\)

ko có âm à nha

1 a)  23/10

   b) 4/5

 2 huệ : 15

   lần  : 21

không  có bài giải thì còn lâu mới tích  

\(\frac{4}{5}.\frac{3}{7}+\frac{4}{5}.\frac{6}{7}-\frac{4}{5}.\frac{4}{14}\)

\(=\frac{4}{5}.\left(\frac{3}{7}+\frac{6}{7}-\frac{4}{14}\right)\)

\(=\frac{4}{5}.1\)

\(=\frac{4}{5}\)

\(\frac{4}{5}\times\frac{3}{7}+\frac{4}{5}\times\frac{6}{7}-\frac{4}{5}\times\frac{4}{14}\)

\(=\frac{4}{5}\times\left(\frac{3}{7}+\frac{6}{7}-\frac{4}{14}\right)\)

\(=\frac{4}{5}\times1\)

\(=\frac{4}{5}\)

x=14

#Hk_tốt

#Ngọc's_Ken'z

\(5\times x-x+6\times x=140\)

\(5\times x+x\times1+6\times x=140\)

\(\left(5-1+6\right)\times x=140\)

\(10\times x=140\)

\(x=140:10\)

\(x=14\)

a,C1 
 (5/6 + 5/8) x 2/3
= 35/24 x 2/3
=35/36
C2
 (5/6 + 5/8) x 2/3
= 5/6x2/3 + 5/8x2/3
= 10/18 + 10/24
= 35/36

b,C1
7/5 x 3/4 - 1/2 x 3/4
= 21/20 - 3/8
= 27/40
C2
7/5 x 3/4 - 1/2 x 3/4
=3/4 x (7/5-1/2)
=3/4x9/10
=27/40

a, 5/6 x (1/8x2/3) 

=5/6 x 1/12

=5/72

b,(7/5 - 1/2) x 3/4 

=0,9 x 3/4

=3,06

c,(5/6+5/8) x 2/3

=70/48 x 2/3

=35/36

a, 5/6 x (1/8x2/3) 

=5/6 x 1/12

=5/72

b,(7/5 - 1/2) x 3/4 

=0,9 x 3/4

=3,06

c,(5/6+5/8) x 2/3

=70/48 x 2/3

=35/36